Heretofore employed is a technique of covering the opening of an article with a paper seal and, if desired, peeling the paper seal to open the opening. For example, a paper seal is stuck to the opening of a container filled with a powdery substance such as instant coffee, detergent or the like, and the paper seal is peeled to take out the powdery substance through the opening. Ordinary sealing is attained by applying a paste to the back of a paper seal, and putting the paper seal to the edge of the opening of a container body. An ordinary instant coffee container has a cap to be screwed and fitted to the container body, and an ordinary powdery detergent container has a cap linked to the container body via a hinge; and they are so planned that the cap covers the entire opening sealed up with a paper seal.
As the paper seal, for example, there are known those having a layer constitution of plastic film/paper or plastic film/aluminium foil/paper or the like (this is referred to as “conventional layer constitution 1”) and those having a layer constitution of paper/plastic film/paper (this is referred to as “conventional layer constitution 2”). Examples of the conventional layer constitution 1 include a paper seal having a layer constitution of oriented polypropylene (OPP) having a thickness of 25 μm/wax having a unit weight of 15 g/m2 and glassine paper having a unit weight of 26 g/m2; and a paper seal having a layer constitution of moisture-proof cellophane/LDPE having a thickness of 20 μm/glassine paper having a unit weight of 25 g/m2. Examples of the conventional layer constitution 2 include a paper seal having a layer constitution of glassine paper having a unit weight of 25 g/m2/LDPE having at thickness of 20 μm/glassine paper having a unit weight of 25 g/m2. These are to be stuck to openings on the side of the glassine paper thereof (Patent Reference 1).
Patent Reference 1: JP-UM-B 2-32567